This invention relates to a system for controlling the release of fuel vapors into the atmosphere from the fuel filler pipe of a vehicle's fuel tank.
As currently designed, vehicle fuel tanks normally operate under a positive pressure. Accordingly, when the filler cap for such a tank is removed, fuel vapors are released into the atmosphere. Similarly, as the tank is filled with fuel, fuel vapors in the tank are forced out of the tank into the atmosphere by the incoming fuel. The release of fuel vapors into the atmosphere under these conditions is undesirable for both environmental and health reasons.
The present invention is directed to controlling the release of fuel vapors into the atmosphere under the foregoing conditions. Specifically, rather than allowing the vapors to escape, the invention routes them to a vehicle-mounted, vapor capture device, such as, a charcoal canister, from which the vapors can be later removed and safely burned in the vehicle's engine.
In addition to controlling vapor escape, the invention also prevents liquid fuel from flowing into the vapor capture device during filling of the fuel tank. Moreover, the invention provides automatic relief for over pressure conditions within the vehicle's fuel tank, is easy to construct, reliable, crash-worthy, and can be readily installed in place of conventional filler pipe assemblies.
In addition to the foregoing, an important application of the invention is to the problem of expulsion of liquid fuel from a vehicle fuel tank after removal of the filler cap. Such expulsion is known to occur for certain vehicles when fuels having an elevated volatility are used or when the vehicle is operated under conditions which result in significant heating of the liquid fuel in the fuel tank. For example, fuel expulsion has been observed for ambulances operated during hot weather and for vehicles in which parts of the exhaust system lie particularly close to the fuel tank.
The expulsion is caused by rapid vaporization of hot fuel in the tank after the pressure in the tank has been released through removal of the filler cap. Depending on the design of the tank and the tank's filler pipe, the amount of fuel left in the tank, and the orientation of the vehicle, such vaporization can eject significant amounts of fuel out of the tank and onto the person who removed the cap. This is obviously a highly dangerous and potentially lethal event and in practice has been found to be an extremely difficult problem to solve for those vehicles which exhibit the problem.
As discussed below, the present invention solves the problem while at the same time providing reliable venting of the fuel tank during normal operation and reliable shut-off of service station fuel pumps during filling of the fuel tank.